Apparatus for pulverizing and classifying materials



H. G. LYKKEN APPARATU$ FOR PULVERIZING AND CLASSIFYING MATERIAL FiledJan. 16, 1959 4 Sheets-Sheet l FIG].

INVENTOR.

. LY KEN 3 B 2 R I o 4 M 4 .Q m 4 4 3 3 .M 72 l O 7 9 l. M X I M I. n|l.vl W 7 u an Y M n w d J 2w M QM 4 M I. 5 N1 2 a I] A 5 5 J a 5 6 J 4HENRY ATTORNEY.

H. G. LYKKEN Dec. 8, 1942.

APPARATUS FOR PULVERIZING AND CLASSIFYING MATERIAL Filed Jan. 16, 1939 4Sheets-Sheet 2 FIG FIG.-3

INVENTOR. HENRY G. LYKKEN ATTORNEY.

H. G. LYKKEN Dec. 8, 1942.

APPARATUS FOR PULVERIZING AND CLASSIFYING MATERIAL Filed Jan. 16, 1939 4Sheets-Sheet 5 INVENT OR.

. VK K E N ATTORNEY.

HENRY c; BY 7 H. G. LYKKEN 2,304,264

Fi led Jan. 16, 1959 '4 Sheets-Sheet 4 APPARATUS FOR PULVERIZING ANDCLASSIFYING MATERIAL Dec. 8, 1942.

INVENTOR. HENRY KE I I v ATTORNEY.

Patented Dec. 8, 1942 UNITED STATES PATENT OFFICE APPARATUS FORPULVERIZING Ann cmssmrmo MATERIALS Henry G. Lykken, Minneapolis, Minn.Application-January 16, 1939, Serial No. 251,062

' .14 Claims.

.My invention relates tonew and improved apparatus for pulverizing andfor classifying friable material, i. e., so as to deliver from theapparatus all particles of pulverized material smaller than adeterminable particle size. a

More specifically, my invention relates to such apparatus whereinpulverization and classification each occurs in a vortex of air andsuspended material. Throughout this specification and classificationapparatus can be part of the same housing or they may be separate,interconnected units.

In the pulverization of friable materials, there are manyfactors whichadversely affect the emciency of pulverization per unit of power input.Of course, the chemical nature and physical structure of the material,its specific gravity, the ratio of mass to weight of particles ofmaterial, the size of the material fed to the pulverizing chamber, andthe degree and amount of pulverization desired all must be considered inthe design of the apparatus. Additionally, some factors affectingefilciency are adequate and even distribution of material to bepulverized throughout the vortex, the prompt and complete removaltherefrom of all material that is sufficiently pulverized, the returnthereto of any oversize particles that escape from the pulverizingvortex so as not to interfere with the'pulverizing action'or-the rgovalof the sufficiently pulverized material, e

In the classification of pulverized material, it has heretofore beenproposed to use the vortex action for classification because, in avortex, material is acted upon according to-its mass and the velocity ofthe vortex, and the oversize material thus will be thrown to the outsideof the vortex and the material of desired size will remain in or findits way to the center of the vortex, from-which it can be removed whilethe oversize is returned tothe pulverizing chamber for furtherpulverization.

Also, means heretofore have been provided for maintaining the velocityof the vortex with or without creating turbulence in the vortex. Again,many of the same factors, referred to above,

adversely affect the efilciency of the "classifier action. Usually thedeslderatum is to deliver as much pulverized material as possible of theselected particle size, i. e., with a very small amount of finestherein, and, for many purposes,

it is essential that no particles larger than the selected size escapefrom the classification chambet with the finished material.

Broadly speaking, it is the object of my invention to providepulverization and classification i5 apparatus of the indicated characterwhich will operate efilciently in handling large quantities of materialwith any desired selected size delivered from the machine, even withextremely fine particles.

It is another object of my invention to provide apparatus of the aboveindicated character in which changes and adjustments can be quickly andsimply made so as to accommodate the machine to handling diflerent typesof material or to deliver different selected particle sizes.

It is still another object of my invention to provide pulverizingapparatus of the indicated character with an improved form of rotor forcreating the pulverizing vortex.

It is still another object of my invention to provide a classificationchamber in which there is an upwardly spiralling vortex feeding into anopen end type of rotor.

It is a further object of my invention to provide a machine in whichpulverization and classification occur wherein the material ispulverized in a vortex of air and suspended material, the vortex passesinto a free vortex zone for preliminary classification and then into azone having a centrifugal action at a right angle to the axis of thevortex to remove the remaining particles above a pre-determined size.

. It is a still further object of my invention to provide an apparatusfor classifying pulverized accurate classification is obtainedefiiciently with relatively low speed whirling action. It is a stillfurther object of my invention to provide a pulverizing and classifyingmachine slfication chamber while maintaining emcient material toextremely fine particle sizes in which ble, in which it is easy to cleanor replace parts,

and which is simple and eilicient in operation.

Other and further objects and advantages of my invention will appearfrom the following specification taken in conjunction with the ac--companying drawings, in which- Figure 1 is a vertical longitudinalsection of a pulverizing and classifying machine, showing one embodimentof my invention;

Fig. 2 is a cross section of such apparatus taken on the line 2-2 ofFig. 1, showing the rotor of the pulverizingchamber;

Fig. 3 is also a cross section of such apparatus, taken on the line 3-4of Fig. 2, showing the rotor in the upper classification zone:

Fig. 4 is a longitudinal section of a classifier, showing a modifiedform of rotor: and

Fig. 5 is a longitudinal section of a further modified form ofclassifier.

The embodiments of my invention shown in the drawings have beensuccessfully operated, but they are shown here purely by way ofillustration of the principles involved, my invention not being limitedto such forms.

Referring to Figs. 1, 2 and 3, the combined pulverizing and classifyingmachine comprises a base I l, upon which is mounted a cylindrical casingl2, the casing being closed at its top by a plate l3. A rotatable shaftl4, driven by any suitable source of power, is mounted in bearings l5and i6, respectively located in the base and top plate. Secured withinthe casing "and spaced above the base ii is a dish-shaped bottom platel1 having a central opening l8 therein. The casing has an air inletopening l9, communicating with the space between the base H and bottomplate I1. Either the opening l8 or the opening I9 is to be provided withsuitable means for controlling the amount of air which can be drawn intothe machine, as hereinafter described, one such means being illustratedby the slide 2i movable in'guides MA to vary the size of opening I8.

A pulverizing rotor is carried by the shaft M adjacent the plate I1, andis of the closedend type. The rotor frame comprises a hub 22, fast uponthe shaft It, to which are secured upper and lower discs 23 and 24 andbetween which are mounted a plurality ofradially extending supports 25.The disc 241s of larger diameter than the upper disc 23 and these discsare slotted to receive the radial supports 25, which extend beyond thebottom of the plate 24 to form fan blades 21 between the disc 24 andplate II. The lower edges of the blades 21 are shaped to conform to theinclination of the bottom plate II. It will be noted that the supports25 do not extend beyond the edges of the plates 23 and 24. Bolted toeach of the supports 25 are removable blades 28 which constitute theblades of the pulverizing rotor. The outer edges of the blades 28 areinclined as indicated at 29, so as to form a tapered rotor. As explainedabove, various materials require diflerent degrees of pulverizingtemplated in this connection blades 28 having other angles ofinclination may be interchanged upon the rotor frame as may be bestadapted for the particular use of the machine, or that the positions ofthe blades 28 upon the radial supports 25 may be varied so as to varythe angle of inclination of the rotor blades. In Fig. 1, the blades 28are wider than the radial supports, and extend slightly beyond the outeredges of the discs 23 and 24. This projection may be more or less thanindicated, both for the entire blade, or for either end thereof.However, I prefer to have the rotor function as a closed end rotor toproduce a violent vortex action almost entirely in the annular zonearound the rotor, and neither the air or material passes through therotor.

. In this latter connection, air is fed to the vortex area through theopening 3i, and material is fed directly to the vortex zone through theopening 32. Any suitable feeding means may be used, there beingillustrated in the drawing a conventional screw feed mechanism 33.Preferably, the feed mechanism will be such that the rate of feed willbe controllable in accordance with the requirements of the particularmachine.

The inner surface of the casing i2 has at the lower portion thereof, inthe pulverizing zone, a corrugated liner ll, which is shown asremovable. For most purposes I prefer to use such a liner to retardthematerial circulating in the outer portion of the annular vortex so asto create a greater differential of movement between the particles ofsuspended material circulating therein. To this end the depth of thecorrugations may vary with different materials, but in all cases, thecorrugated liner may be omitted entirely and in some cases it may evenbe preferable to omit it.

In the operation of the pulverizer as described, the material is fedinto the vortex of air created by the rotor, and is carried insuspension in that vortex while being whirled around at high speed. Thecentrifugal forces acting upon the particles will cause a rubbing ofparticles upon each other as well as an impact between particles with acorresponding shifting of the particles about in the vortex as they arereduced in size, thus creating further impacts and further attrition,all as is well known.

However, the upwardly inclined rotor will pro duce' a more violentvortex in the narrow space toward the bottom of the pulverizing zonewhere vortex action created by the rotor and it is conthere is atendencyfor the greatest concentra-' tion of material to be pulverized, and asthe area of the vortex zone increases, by reason of the taper of therotor, the vortex action is a little less violent and more space isprovided for the material as it becomes pulverized'.- Furthermore, thecomponent of the forces produced by the upwardly inclined roto'r aresuch as to cause a more I complete and equal distribution of thematerial throughout the vortex zone. "Additional advan-' tages arisingfrom use of the inclined rotor occur with respect to the return of theoversize material from the classification zone or chamber. the promptinter-mingling of the returned material with the vortex, and in thethorough, complete and prompt removal from the pulverizing zone of thesufficiently pulverized material, all of which matters will be morefully discussed hereinafter. v r

In the embodiment shown in Figs. 1 and 3, the classification chamber isdefined by a smoothsurfaced inner casing II which is of less diameterthan the outer casing l2 and is held spaced therefrom by any suitablemeans, such as the spacing rings 40. The chamber comprises a free zone4| at one end thereof, in which there is no mechanism, and a zone 42 atthe other end of the chamber in which is located a rotor 43. The upperend of the classification chamber is closed by a ring shaped plate 44having a central opening 45 therein which constitutes the outlet fromthe classifier.

This outlet communicates with the chamber 45 between the ring shapedplate 44 and the top plate I3 from which is a discharge opening into anoutlet pipe 41 for the finished material.

The rotor in the classification chamber consists of a lower disc 48having a central inlet opening 49 therein, a top disc having a centraloutlet opening 52 therein, and a plurality of radially disposed blades53 which are mounted upon a hub 54. The discs 48 and 5| and blades 53are secured together in any appropriate manner, as by welding, and thehub 54 is fast upon the shaft l4 so as to rotate therewith.

The top disc 5| of the rotor 43 larger in separation by the vortex rotor43 during all of which time t or removal of the oversize particl iscontinuing progressively so that by thetime the material-laden air inthe vortex reaches the opening 49, the greater portion if not all of theoversize material has been thrown out toward the outside of the casingand beyond the limits of the opening 49. The air and the remainingmaterial carried therein enters the opening 49 where the air andmaterial is given a whirling motion by the rotor 43 and is subjected tothe centrifugal forces. generated by the rotating fan blades 53.

. The action and proportioning of the various the additional centrifugalforce imparted by the diameter than the bottom disc 48 and extends veryclose to the inner casing 39 as well as close to the ring-shaped plate44. In order to prevent any leakage of air and material to the outlet 45through the space between the plate 44 and disc 5|, the top surface ofthe disc may be provided with small radial ribs 55 to act as fan bladesexerting a centrifugal pressure outwardly toward the inner casing 39.

The.chamber-48 is, in this embodiment, a fan chamber as well as anoutlet chamber. The chamber has two fans therein, the fan 55 and the fan51. The fan 56 has a plurality of blades 53 which, in the structureindicated in Fig. 1,

are reduced extensions of the blades 53 of the classifier rotor, the hub54 also being extended upwardly to carry the blades 58. At the upper endof the blades 58 is a top disc 59 to which the blades are secured in anysuitable manner.- The fan 51 comprises a plurality of blades 5| mountedradially upon a ring shaped plate 62 which in turn is secured to thedisc 59. .{I'he fans 55 and 51 act as suction fans to draw the air andthe material suspended therein through the pulverizing and classifyingchambers, but such suction apparatus need not be located in the casingat all, and may be a suitable suction device entirely separate anddistinct from the pulverizing or classifying mechanism as shown, forexample, in my prior Patent No. 1,760,245, issued May 27, 1930, theshowing of the drawings being a present preferred arrangement that issatisfactory for most materials.

The operation of the classifier can be described as follows: The highspeed vortex created by the pulverizing rotor discharges or spiralsupwardly from the annular pulverizingzone into the lower chamber 4|carrying with it pulverized and some partially pulverized ,or oversizematerial. In the rotor 43 to be thrown outwardly toward the inner casing39 at right angle to the normal path through the rotor. Furthermore, theproportioning is such that most of the air leaves the classifierthroughthe outlet 52 of the rotor.

, Such air as is thrown laterally by the rotor passes around the edge ofthe bottom disc 48 and recirculates through the opening 49. Hence anysumciently pulverized material which may have been thrown outaccidentally by the rotor 43 is carried back into the opening 49 andfinds its way out of the machine with the upwardly rising currents ofair. In this connection, it will be noted that the blades 53 of therotor do not extend to the edge of the disc 48, which arrangement Iprefer so as to overcome any tendency for turbulences at the edge of therotor. Also,-

the size of the disc 48 may be different, which will vary the amount ofrecirculation, and is a desirable control. However, since the action ofthe rotor 43 is in the same direction as the vortex in the free zone 4|.the air and material discharged radially from the rotor is receiving animpetus from the fan blades in the direction of the vortex thus tendingto maintain the vortex action in the classification chamber.

The discharge pipe 41 of the machine may be connected either to acollector, such as a cyclone collector, or directly to some point of usefor the pulverized material.

The classifier action and operation has been described in connectionwith the mechanism as shown, in which the inlet opening 49 to the rotor43 is approximately the same size as the outlet openings 52 and 45. Thevelocity of the material laden air moving through the fan 43 can becontrolled by controlling the relationship of these inlet and outletopenings from a relationship where the inlet opening is considerablysmaller than the outlet, to the relationship where the vertical vortextype of machine shown in Fig. 1, 4

' 4| toward the eye or inlet opening 49 of the inlet would beconsiderably smaller than the opening 49. In this latter case the airand material might even enter the rotor 43 principally at the top of thepulverizing chamber so that there is a wide space for the entrance ofthe re- Jected material. This wide space is likewise useful to allowready removal of the pulverized material from the vortex zone withoutbeing impeded by-the returning rejected material. Furthermore, thispermits of aeration of the retuming material by the upwardly moving airso that any completely pulverized particles which may be clinging to theoversize material will be removed and carried back into theclassification chamber. Additionally, the inclination'of the rotorblades permits of a better distribution of the returning material in thepulverizing vortex because it will be subjected to the action of alarger part of the blades than if the rotor were of uniform diameter.

In'the arrangement and proportioning of this entire apparatus largevolumes of air may be carried through both the pulverizing chamber andthe classification chamber so that the material that is sufficientlypulverized is promptly carried out of the pulverizing chamber, throughthe classification chamber, and out of the machine with the result thatthe delivered product zontal rotor type of machine shown for example.

in my Patent No. 1,838,560, issued December 29, 1931, or in conjunctionwith a machine where a vortex is created by air jets as shown in myprior Patents Nos. 1,756,254 and 1,768,621, issued respectively April29, 1930, and July 1, 1930, or with any other pulverizer mechanism.Also, the air-suspended material may be caused to whirl in theclassifier by other means than the pulverizing rotor as, for example,being introduced into the classifier mechanism in such direction as tocreate a vortex in the free zone 4|, as indicated in my prior Patent No.1,753,437, issued April 8, 1930.

The; casing of the apparatus illustrated in Figs. 1, 2 and 3 isapproximately fifty-four inches high and twenty-four inches in diameter,and pulverizes several hundred pounds of materials -per hour using arotor speed of approximately twenty-two hundred revolutions per minute.The

free zone 4| is shown as having considerable height, but I have usedsuccessfully a machine of this construction having twelve inches lessheight, as well as machines of greater dimensions. Likewise, the drivefor the shaft l4 may be either through the top or the base of themachine, as indicated in the co-pending application of Lykken andLykken, Serial No. 285,484, filed July 20, 1939. I prefer to drive theshaft through belts and pulley, such as pulley 65 shown in Fig. 1, aswill be understood. It will be evident that any other form of drive andmethod of speed variation could be. used. Also, in some instances theinner casing 39 may be omitted.

Also, the pulverizing rotor is shown with eight blades and theclassifier rotor as having four blades but the number of blades used oneach of these rotors may be varied as may be found necessary ordesirable for the particular problem in hand.

It should be pointed out that the present in vention contemplates adrive for the classifica-' tion rotor that is independent of the drivefor the pulverizing rotor so that the speed of the classifier rotor maybe varied from the speed of the pulverizing rotor as one means ofregulating the degree of'classification or separation in accordance withthe requirements of the particular case in hand.

Fig. 4 illustrates a classifier such as may be used with other types ofpulverizing mechanisms than the vertical rotor type shown in Fig. 1,although, of course, the principles may also be used in thatconstruction also. In this case there is shown a modified form ofclassification rotor.

The classification apparatus comprises a casing ll having a lowerentrance portion 12, with an inlet opening 13 at the bottom thereof, anda top plate I4. closed by a ring-shaped plate 19, corresponding to thering-shaped plate 44, and is spaced from the top plate 14 so as to forma combined fan and outlet chamber 16. The classification chamber has afree vortex zone 11 at the lower end thereof, and an upper zone 19 inwhich is located the rotor 19. The rotor 19 is mounted upon a shaft Mwhich is driven by any suitable source of power (not shown).Air-suspended pulverized material enters the classification chamberthrough the opening 13 and preferably in a manner to produce a vortex inthe air and material. 1

In the lower portion of the free zone 11 a rotor in the form of a fiatdisc 92 may be mounted .upon the shaft 9| so as to be rotated therewith.The disc 92 performs two omces, first, it prevents a direct entrance ofthe air-suspended material into the opening or eye 94 of the rotor 79and, secondly, it imparts an impetus to the vortex of air and materialso as to increase or maintain the speed thereof in the zone Il withoutimparting any turbulence thereto. I

The rotor 19 comprises a lower disc 99, in which is the inlet opening84, and an upper disc 86, in which is an outlet opening 91 that com-'municates with the outlet opening 99 from the classification chamber tothe fan and outlet chamber 16. It will be noted that the bottom disc 85of the rotor 19 extends more closely to the inner surface of the casingll than does the bottom disc 48 of the rotor shown in Fig. 1. The rotorI9 has a plurality of radial blades 99 which are mounted upon a hub 9|and to which the discs 95 and 96 are secured. Again in this structure areduced portion of the blades. 99 extend through the openings 91 and 99into the fan chamber 19 to form the fan 92. The fan chamber also has afan 93 corresponding to the fan 51 shown in Fig. 1. i

In the form shown in Fig. 4, the rotor blades 89 are slottedhorizontally for the reception of a fiat disc 94 which is secured to theblades and also to the hub 9|. The disc 94 extends transversely of and asubstantial distance across the openings 94, 91 and 99. The material tobe delivered from the classifier enters the chamber 16 through theopening 99 and is delivered from the machine through the outlet 99 to acollector or to a place of use as the case may be.

The operation of the classifier is somewhat similar to the operation ofthe classifier described in Fig. 1, in that there is a free vortex zone11 in which the primary classification takes place and the coarsermaterial is thrown outwardly, while th finer material and air enters theeye 94 of the rotor 19 where it is subjected The classification chamberitself is to the centrifugal throw-out action of the blades 89 to removeany oversize particles which may not be eliminated in the vortex actionin the free zone 11. However, in the modification shown in Fig. 4, thepurpose of the disc 94 is to force all of the air and material away fromthe axis of the fan I9 so as to be subject to the greater centrifu-' galforce exerted by the outer ends of the fan that obtained with muchhigher speeds of rotation with the type of classifier rotor shown inFig. l for example, or by other forms of vortex classifiers heretoforeused in the art. Addltionally, there is even less likelihood of anystray particles of oversize material escaping from the classification.chamber through the outlet 00.

Conversely, by the addition of such a disc as illustrated at 94 in Fig.4 to the higher speed rotors, such as shown in Fig. 1, it is possible todeliver from the classifier practically impalpable powder free of anyoversize particles.

Fig. 5 illustrates a further modification of the arrangement in theclassification chamber, the same being shown applied to a classifiersimilar to that shown in Fig. 4, and duplicate parts of operation anduse will not be described. In the form shown in Fig. 5, the classifierrotor comprises a bottom disc IOI having an inlet opening I02 therein, atop' disc I03, and a plurality of radial blades I 04 mounted upon ahubI05 that is fast upon the rotatable shaft I06. Mounted below the bottomdisc I M of the classifier rotor is a disc I01 carried by a hub I08which is fast upon the shaft I08, as by means of a set screw, but whichmay be adjusted vertically along its length to be closer to or moreremoved from the inlet I02. The purpose of this disc I01 is three-foldin that (1) it prevents a direct vertical entrance of the air-suspendedmaterial into the rotor blades I04 along the shaft I06, and for aconsiderable distance laterally thereof, (2) it imparts a higherrotative speed to the vortex as it is about to enter the eye I02 of theclassifier rotor so as to reject oversize material just prior toentering that rotor; and (3) it controls the amount of air entering theclassifier rotor and hence the amount of air that is recirculatedbetween the zone III of that chamber and the free zone II2. That is tosay, the less amount of air that is permitted to enter the classifierrotor. the less there will be discharged laterally therefrom andrecirculated, because of the demands of the suction fan II3 whichcorresponds in operation to the fan 56 of Fig. l and 92 of Fig. 4.

This recirculation can be controlled from the instance where the discI0! is very close to the bottom disc IN, to the condition where it is sofar removed therefrom that substantially the full quantity of air andmaterial can enter the eye I02 of the fan. The use of this disc I0'Ialso enables the obtaining of desired fine classification withrelatively low speeds of rotation of the classifier rotor, andcontrolling the recirculation of air be- Other and further modificationsmay be made in the arrangement and location of parts within the spiritandscope of my invention, and such modifications are intended to becovered by the appended claims.

I claim:

1. A pulverizing and classifying chamber comprising a casing, air andmaterial inlets thereto. a closed end rotor operating adjacent one endof the casing to produce a pulverizing vortex of airsuspended material.the rotor having radial blades arranged to form a tapered rotor, anout-. let at one end of the casing. means for drawing air andpulverizing material through said casing and outlet, and a classifyingzone having two communicating portions, one having a substantiallysmooth wall in which the vortex of air and pulverized material rotatessubstantially free from turbulence, and the other receiving the airsuspended material from the first portion and having therein adjacentthe outlet means for subjecting the air and pulverized material to afurther centrifugal action on its passage to the outlet, to rejectoversize material and return the same to the casing for furtherpulverization.

2. A pulverizing and classifying chamber comprising a tubular casing,air and material inlets .thereto, a closed and rotor operating adjacentone end of the casing to producea pulverizing vortex of air-suspendedmaterial, the rotor having radial blades arranged to form a taperedrotor, an outlet at one end of the casing, means for drawing air andpulverized material through saidcasing and outlet, and a classifier forthe pulverized material having a bladed rotor mounted adjacent theoutlet end of said casing, said rotor having axial inlet and outletopenings, there being a substantially uninterrupted portion of saidcasing between said rotors in which portion the vortex of air andpulverized material rotates, the classifier rotor communicating at itsperiphery with the intermediate portion of the casing.

3. A pulverizing and classifying machine comprising a casing, air andmaterial inlets thereto. a closed end rotor operating adjacent one endof the casing to produce a pulverizing vortex of airsuspended material,the rotorv having radial blades arranged to form a tapered rotor, anoutlet at one end of the casing, means for drawing air and pulverizedmaterial through said casing and outlet, and a classifying zone having asubstantially uninterrupted portion into which the vortex of air andpulverized material is introduced and rotates substantially free fromturbulence, and a second portion having therein a rotor mounted adjacentthe outlet, said rotor comprising spaced apart top and bottom discshaving axial openings therein, a hub, and radial blades extendingbetween said discs, the blades having a shorter radius than the bottomdisc.

4. A pulverizing and classifying chamber comprising a casing, air andmaterial inlets thereto, a closed end rotor operating adjacent one endof the casing to'produce a pulverizing vortex of airsuspended material,the rotor having radial blades arranged to form a tapered rotor, a platedividing the casing into a classifying zone and a fan-containing zone,the plate having a central outlet opening therein, and a rotor mountedadjacent the outlet opening and having a hub and a plurality of bladesmounted thereon extending through saidoutlet opening and both above andbelow said plate.

5.-A classifier for pulverized material comprising a cylindrical casingof substantial height,

means for producing in the lower part thereof a vortex of air-suspendedpulverized material, an

into the casing beneath the rotor and into the inlet opening.

6. A classifier for pulverized material comprising a casing, meansadmitting air and material thereto for classification of the material,an outlet therein, a hub mounted in the casing,-and a rotor mounted onsaid hub, said rotor comprising bottom and top discs respectively havingaxial inlet and outlet openings, and a plurality of blades extendingacross the openings and between the discs, the rotor communicating aboutits periphery with the interior of the casing. and a plate mounted insaid casing and operatively associated with said rotor, said plateextending transversely of said openings.

7. A classifier for pulverized material comprising a casing, meansadmitting air and material thereto for classification of the material,an outlet therein, a hub mounted in the casing, and a rotor mounted onsaid hub, said rotor comprising bottom and top discs respectively havingaxial inlet and outlet openings, a plurality of blades extending acrossthe openings and between the discs, the rotor communicating about itsperiphery with the interior of the casing, and a plate mounted betweenthe top and bottom discs and extending a substantial distancetransversely of said openings;

8. A classifier for pulverized material comprising a casing, meansadmitting air and material thereto for classification of the material,an outlet therein, a hub mounted in the casing, and a rotor mounted onsaid hub, said rotor comprising bottom and top discs respectively havingaxial inlet and outlet openings, a plurality of blades extending acrossthe openings and between the discs, the rotor communicating about itsperiphery with the interior of the casing, and means cooperating withthe rotor to divert material a, substantial distance toward theperiphery of the rotor as it passes through the openinga 9. A classifierfor pulverized material comprising a casing, means admitting air andmaterial -thereto for classification of the material, an outlet in thecasing, a hub mounted in the casing, and a rotor mounted on said hub,said rotor comprising bottom and top discs respectively having axialinlet and outlet openings, a plurality of blades extending across theopenings and between the discs, the rotor communicating about itsperiphery with the interior of the casing, and an adjustable platepositioned to control admission of air and material to said inletopening.

10. A classifier for pulverized material comprising a casing, meansadmitting air and material thereto, an outlet therein, and a rotormounted in the casing, said rotor comprising bottom rial thereto forclassification of the material, an

outlet in the casing, a hub mounted in the casing, and a rotor on saidhub, said rotor comprising bottom and top discs respectively havingaxial inlet and outlet openings, a plurality of blades extending acrossthe openings and between the discs, the rotor communicating about itsperiphery with the interior of the casing, and means cooperating withthe inlet and outlet openings of the rotor to control the amount of airdischarged into the casing peripherally of the rotor andrecirculated tothe inlet opening.

l2.-A classifier for pulverized material comprising a casing, means forproducing a vortex of air-suspended pulverized material in the lowerportion thereof, an outlet in the casing, 'means for drawing air andmaterial through said outlet, a rotor mounted adjacent the outlet, saidrotor having radialv blades, an axial inlet communicating with thecenter portion of the vortex. and an outlet opening, and means mountedadjacent the rotor inlet for increasing the speed of the vortex as it isabout to enter the rotor inlet and to control the amount of air admittedto said inlet.

13. A classifier for pulverized material comprising a tubular casing, anoutlet therefrom, a hub mounted .for rotation in said casing, and arotor carried by the hub near said outlet and of lessdiameter than saidcasing, said rotor comprising a bottom disc having'an axial opening. anda plurality of blades extending radially from said hub across saidoutlet opening in proximity thereto and a substantial distance alongsaid hub forming pockets communicating with said outlet and saidopening, the undesired material entering therotor through said openingand being discharged peripherally of said rotor.

14. 'A classifier for pulverized material comprisinga tubular casinghaving two zones therein, means for producing a vortex of air-suspendedpulverized material in one of said zones, the zone being substantiallyunobstructed so that the vortex operates therein substantially fee fromturbulence, 'a rotor mounted in said second zone, the rotor having abottom disc with a central .opening therein forming an axial inletcommunicating with the center portion of said vortex the rotor alsohaving an axial outlet and communicating with said zone about itsperiphery, and an outlet from said casing for pulverized material.

' HENRY G. LYKKEN.

